Agricultural apparatus for spraying fields with mixtures of seed, water, mulch and/or fertilizers have been well-known for many years. Most of these systems include a vehicle-mounted tank holding the mixture; a pump; a discharge nozzle for spraying the mixture; and hosing for delivering the mixture under pressure (via the pump) from the tank to the discharge nozzle. Some of these spraying systems are provided with structure near the pump outlet to cause continuous circulation of the mixture, through the use of special valving, even when the nozzle is not in use, thereby feeding back or recirculating a portion or all of the mixture back to the tank. This is particularly beneficial in facilitating constant agitation of the mixture, preventing stratification or settling out of the mixture's solid particles in the tank and hosing, which would otherwise cause a non-uniform spray and a disproportionate mixture of chemicals.
U.S. Pat. Nos. 2,878,617 to Finn; 3,147,922 to Warner; 3,512,713 and 3,638,860 to Carlyon, Jr., all disclose vehicle-mounted agricultural apparatus for spraying mixtures of solid and liquid materials composed of seed, mulch, water and/or fertilizer, including a tank; a pump; a discharge nozzle; and hosing for delivering the mixture, under pressure via the pump, to the discharge nozzle. These prior art systems are provided with valve means to feed-back or recirculate a portion or all of the mixture to the tank, particularly when the nozzle is not in use. However, while these above-mentioned systems may assure non-clogging of mixture in the system's circulatory path and promote a uniform spray of equal chemical mixture, no means is incorporated to prevent clogging of the mixture at the nozzle or in the nozzle's delivery line.
Consequently, arrangements to eliminate system clogging by continually recirculating the mixture, are unsuccessful in preventing clogging of the mixture at or near the discharge nozzle.